Hydrorefining of petroleum crude oil and catalyst therefor



3 166,494 HYDROREFINENG 01 PETRQLEUM CRUDE H.

AND CATALYST THEREFGR John G. Gatsis, Des Piaines, and William K. T. Glenn, Island Lake, lll., assignors to Universal Oil Products Company, Des llaines, ill., a corporation of Delaware No Drawing. Filed Aug. 17, 1962, Ser. No. 217,552

6 Claims. (Cl. 2tl8264) The present invention relates to a method forpreparing a novel catalyst particularly adaptable for utilization in the process of hydrorefining petroleum crude oils, heavy vacuum gas oils, heavy cycle stocks, crude oil residuum, topped crude oils, and other heavy hydrocarbon mixtures boiling above the normal gasoline boiling range. More specifically, the present invention involves a process for hydrorefining a petroleum crude oil for the purpose of effecting the removal of nitrogen and sulfur therefrom, affording unexpected advantages in the destructive removal of organo-metallic contaminants and the conversion of pentane-insoluble hydrocarbonaceous material within the petroleum crude oil.

Petroleum crude oils, and the heavy hydrocarbon fractions and/or distillates obtained therefrom, particularly heavy vacuum gas oils and topped crudes, contain nitrogenous and sulfurous compounds in exceedingly large quantities. In addition, petroleum crude oils contain detrimental quantities of organo-metallic conatminants which exert deleterious effects upon acatalyst utilized in various processes to which the crude oil, topped crude oil, or heavy hydrocarbon fraction may be subjected. The more common of these metallic contaminants are nickel and vanadium, generally existing in concentrations in excess of about 50 p.p.m., although other metals including iron, copper, etc., are often present. Metallic contaminants may occur within the petroleum crude oil in a variety of forms; they may exist as metal oxides or sulfides, introduced into the crude oils as metallic scale or particles; they may be present in the form of soluble salts of such metals; usually, however, they exist in the form of organo-metallic compounds such as metal porphyrins and the various derivatives thereof. Although the metallic contaminants, existing as oxide or sulfide scale, may be removed, at least in part, by a relatively simple filtering technique, and the Water-soluble salts are at least in part removable by washing and a subsequent dehydration procedure, a much more severe treatment is required to etlect'the destructive removal of the organo metallic compounds, partitcularly to the degree necessary to produce a crude oil or heavy hydrocarbon fraction which is suitable for further processing.

In addition to the organo-metallic contaminants, including metal porphyrins, crude oils generally contain greater quantities of sulfurous and nitrogenous compounds than are found in lighter, normally liquid hydrocarbon fractions such as gasoline, kerosene, light gas oil, etc. For example, a Wyoming sour crude, having a gravity of 23.2 API at 60 F., contains about 2.8% by Weight of sulfur and 2700 p.p.m. of nitrogen, 18 p.p.m. of nickel and about 71 p.p.m. of vanadium. The nitrogenous and sulfurous compounds are converted, upon being subjected to catalytic hydrorefining, into hydrocarbons, ammonia and hydrogen sulfide; similarly, any oxygenated compounds will be converted into Water and the hydrocarbon counterpart. However, a reduction in the concentration of the organo-metallic contaminants is not as easily achieved, and to the extent that the same no longer exert a detrimental effect with respect to further processing of the petroleum crude oil, or fraction thereof. Notwithstanding that the total concentration of these metallic contaminants may be relatively small, for example, less ted States Patent 0 than about 10 p.p.m. of metallic porphyrins, calculated as the elemental metals, subsequent processing techniques will be adversely affected thereby. Thus, when a hydrocarbon charge stock, containing metals in excess of about 3.0 p.p.m., is subjected to a cracking process for the purpose of producing lower-boiling components, the metals become deposited upon the catalyst employed, steadily increasing in quantity until such time that the composition of the catalytic composite is changed to the extent that undesirable side eilects result. That is to say, the composition of the cracking catalyst is controlled with respect to the nature of the charge stock being processed and to the desired product quality and quantity. This composition is changed considerably due to the deposition of the metallic contaminants thereupon, the changed composite resulting in changed catalytic characteristics. This particular eifect is highly undesirable with respect to the cracking process since the deposition of metallic contaminants upon the catalyst also tends to result in a lesser quantity of valuable liquid product, in large amounts of hydrogen and coke, the latter also producing a relatively rapid degree of catalyst deactivation.

In addition to the foregoing contaminating influences, petroleum crude oils and other heavier hydrocarbon fractions contain excessive quantities of pentane-insoluble material. For example, the Wyoming sour crude described above consists of about 8.3% by weight of pentane-insoluble asphaltenes, being hydrocarbonaceous compounds considered as coke-precursors and having the tendency to become immediately deposited within the reaction zone and onto the catalytic composite in the form of a high molecular weight, gummy residue. At the conditions of operation necessary to eifect a reasonably efficient, successful process, it is virtually impossible to avoid the conversion of asphaltenic compounds into heavy hydrocarbonaceous coke. Since the deposition of this material constitutes a large loss of charge stock, it is further economically desirable to convert such asphaltenes into useful hydrocarbon oil fractions, thereby increasing the liquid yield of valuable product as based upon the quantity of oil charged to the process.

The object of the present invention is to provide a much more efiicient process for hydrorefining heavier hydrocarbonaceous material, and particularly petroleum crude oils containing pentane-insoluble asphaltenes, utilizing an unsupported catalyst prepared in a particular manner. The term hydrorefining, as employed herein and in the appended claims, connotes the catalytic treatment, in an atmosphere of hydrogen, of a hydrocarbon fraction or distillate for the purpose of eliminating and/ or reducing the concentration of the various contaminating influences previously described. As hereinbefore set forth, metals are removed from the charge stock by deposition of the same on the catalyst employed, and asphaltenes are deposited in the form of coke. This increases the amount of catalyst within the reaction zone, actively shields the catalytically active surfaces and centers of the catalyst from the material being processed, and generally precludes the utilization of an efiicient fixed-bed catalyst system for processing such highly contaminated crude oil. Various moving-bed processes, employing catalytically active metals deposited upon a carrier material consisting of silica and/or alumina, for example, or other refractory inorganic oxide material, such as alumina-zirconia, silica-zirconia, etc., are extremely erosive. causing plant maintenance to become diificult and expensive. The present invention teaches the preparation of a colloidally dispersed, unsupported catalytic material useful in a slurry-type process, which catalytic material will not eifect extensive erosion or corrosion of the reaction system. The present process yields a liquid hydrocarbon product which is more adaptable for further processing without experiencing the difficulties otherwise resulting from the presence of the foregoing contaminants. The present invention affords a process which is particularly advantageous for effecting the conversion of organo-metallic compounds without significant product yield loss, while simultaneously converting pentane-insoluble material into pentane-soluble liquid hydrocarbons.

A broad embodiment of the present invention encompasses a hydrorefining catalyst comprising a colloidal suspension of molybdenum trioxide and phosphoric acid in a hydrocarbon. lvlore specifically, the hydrorefining catalyst of the present invention comprises a colloidal suspension of molybdenum trioxide, phosphoric acid and boric acid in a hydrocarbon, in which suspension the molar ratio of molybdenum to phosphorus is within the range of about 1:1 to about 18:1, calculated as the elements thereof.

Another broad embodiment of the present invention affords a process for hydrorefining a hydrocarbon charge stock, which process comprises initially forming a solution of a molybdenum trioxide and phosphoric acid, commingling said solution with said hydrocarbon charge stock, distilling the resulting mixture to remove water, thereby forming a colloidal suspension of said solution Within said charge stock, and thereafter reacting said colloidal suspension with hydrogen at a temperature above about 225 C. and at a pressure greater than about 500 pounds per square inch gauge.

A more limited embodiment of the present invention involves a process for hydrorefining a petroleum crude oil containing pentane-insoluble asphaltenes, which process comprises forming a solution of molybdenum trioxide, phosphoric acid and boric acid, in which the molar ratio of molybdenum to phosphorus is within the range of from about 1:1 to about 18:1, calculated as the elements; commingling said solution with said hydrocarbon charge stock, distilling the resulting mixture to remove water, thereby forming a colloidal suspension of said solution in said charge stock, and thereafter reacting said colloidal suspension with hydrogen at a temperature within the range of from about 225 C. to about 500 C. and at a pressure of from about 500 to about 5000 pounds per square inch gauge.

From the foregoing embodiments, it is noted that the present invention involves the preparation of a colloidally dispersed, unsupported catalyst within the hydrocarbonaceous material from which the contaminating influences are to be removed. The catalyst is prepared by initially forming a mixture of molybdenum trioxide and phosphoric acid, adding the mixture to the material to be processed. As hereinafter indicated by specific examples, the additional of minor quantities of boric acid to the molybdenum oxide-phosphoric acid solution further enhances the removal of the contaminating influences. The molybdenum oxide and phosphoric acid are employed in amounts such that the colloidal suspension comprises from about 0.1% to about 10.0% by weight of molybdenum, and the molar ratio of molybdenum to phosphorus is within the range of about 1:1 to about 18: 1, and preferably having an upper limit of about 12: 1. When boric acid is employed, the molar ratio of molybdenum to phosphorus to boron is within the range of about 1:121 to about 18:1:1, calculated as the elements.

Briefly, the process is effected, as hereinafter set forth in the specific examples, by initially dissolving the desired quantity of molybdenum trioxide in phosphoric acid or a mixture of phosphoric and boric acids. The resulting solution is then intimately commingled with the petroleum crude oil or other heavy hydrocarbon fraction, from which mixture water is removed, for example by heating the mixture at a temperature sufficiently high to remove the same by distillation. That is to say, the water is removed in a continuous manner as the solution is added to the petroleum crude oil, for example, by adding benzene which forms an azeotropic mixture with water and permits the distillation to be efiected at a sufficiently low temperature. Other suitable solvents, in addition to benzene, would include various alcohols, esters and ketones such as isopropyl alcohol, isopentyl alcohol, methyl alcohol, amyl alcohol, methyl ethyl lietone, ethyl acetate, etc. Temperatures below about 310 (3., and preferably less than C., are preferred for the purpose of removing the water, leaving the molybdenum, phosphoric and boric acids dispersed within the crude oil as a colloidal suspension. The colloidal dispersion is then passed into a suitable reaction zone maintained at a temperature within the range of from about 225 C. to about 500 C. and under a hydrogen pressure within the range of from about 500 to about 5000 pounds per square inch gauge.

Although the exact physical and/or chemical state of the icolloidally dispersed particles is not known precisely, it is believed that the molybdenum trioxide reacts with the phosphoric acid to form a complex which, when added to the petroleum crude oil, in turn forms particles having an uni entified crystalline structure. The hexavalent molybdenum is reduced to a lower valence state in the presence of the phosphoric acid, possibly resulting in a form which resembles molybdenum blue.

When the colloidal suspension is reacted with hydrogen under the aforementioned conditions of operation, the more readily reducible sulfurous compounds are caused to form hydrogen sulfide which reacts with the catalyst particles to produce a new catalyst state believed to be a form of suit ded molybdenum, although X-ray analysis of the used catalyst indicates a somewhat different crystalline structure. The function, or effect, of the boric acid in combination with the phosphoric acid, is equally obscure. It is believed that boron acts as a hetero-atom, forming a heteropoly molybdate different from that which is formed when boric acid is employed with molybdenum trioxide in the absence of phosphoric acid.

The process may be conducted as a batch-type procedure, or in an enclosed vessel through which the colloidal suspension is passed; when effected in a continuous manner, the process may be conducted in either upward flow or downward flow. Normally liquid hydrocarbons are separated from the total reaction zone product effluent by any suitable means, for example, through the use of a centrifuge or settling tanks, at least a portion of the resulting catalyst-containing sludge being combined with fresh petroleum crude oil, and recycled through the reaction zone. In order to maintain a high degree of catalytic activity, it is preferred that at least a portion of the catalyst-containing sludge be removed from the process prior to combining the remainder with fresh crude oil. The precise quantity of catalyst-containing sludge removed from the process will be dependent upon the desired degree of contaminant removal. However, it is desirable to add a quantity of fresh molybdenum oxide-phosphoric acid-boric acid solution to the petroleum crude oil to compensate for that quantity removed from the catalystcontaining sludge, maintaining, however, the concentration of the dispersed material within the crude oil from about 0.1% to about 10.0% by weight of molybdenum.

The following examples are given to illustrate the process of the present invention and the eifectiveness thereof in removing nickel and vanadium contaminating influences from a petroleum crude oil, and in converting the pcntane-insoluble asphaltenes while simultaneously effecting the conversion of sulfurous and nitrogenous compounds into sulfur and nitrogen-free hydrocarbons. It is not intended that the present invention be unduly limited to the reagents, charge stock and/0r operating conditions employed. Spectrographic emission was employed to analyze the normally liquid product etfiuent for the concentration of organo-metallic compounds remaining therein.

The crude oil utilized to illustrate the benefits afforded through the use of the present invention was :1 Wyoming sour crude oil having a gravity of 23.2 API at 60 F.,

containing about 2.8% by weight of sulfur, approximately 2700 p.p.m. of nitrogen, 18 p.p.m. of nickel and 71 p.p.m. of vanadium as metal porphyrins, calculated as the elemental metals. In addition, the sour crude consisted of about 8.3% by weight of pentane-insoluble asphaltenes. As hereinafter indicated, the process of the present invention not only effects conversion of a significant proportion of pentane-insoluble asphaltenes, but also results in a substantial production of lower-boiling hydrocarbons as indicated by an increase in the gravity, API at 60 F., of the normally liquid hydrocarbon portion of the total reaction zone product effluent.

Example I In this example, 5.76 grams of molybdenum trioxide were added to 200 grams of boiling water and heated for minutes. A finely divided slurry of molybdenum trioxide in water resulted, and this slurry was added dropwise to 500 grams of the Wyoming sour crude and 250 grams of benzene, the resulting mixture being continuously distilled during admixing for the purpose of removing water. 200 grams of the resulting colloidal suspension, containing 0.5% by weight of molybdenum, was placed in a rotating autoclave under 100 atmospheres of pressure, the temperature being increased to a level of 400 0., resulting in a final pressure of 200 atmospheres. After 8 hours at these conditions, the total effluent was subjected to centrifugal separation to provide a catalystcontaining sludge and a normally liquid hydrocarbon product. The normally liquid hydrocarbon product, upon analysis, indicated 1990 p.p.m. of nitrogen, 0.68% by weight of sulfur, 1.48% by weight of pentane-insoluble asphaltenes, 2.0 p.p.m. of nickel and 1.6 p.p.m. of vanadium.

In addition to 5.76 grams of molybdenum trioxide, 2.47 grams of boric acid were added to 200 grams of water and heated to the boiling point for 10 minutes. The finely divided slurry was added to 500 grams of the Wyoming sour crude, containing 250 grams of benzene and subjected to distillation during the addition. 200 grams of the resulting colloidal suspension, containing 0.8% by weight of molybdenum, was placed in the rotating autoclave at a temperature of 400 C. and a pressure of 200 atmospheres for a period of 8 hours. The normally liquid product effluent, following centrifugal separation from the total product efiiuent, indicated 2250 ppm of nitrogen, 1.16% by Weight of sulfur, 2.31% by weight of pentane-insoluble asphaltenes, 15.4 p.p.m. of nickel and 4.3 p.p.m. of vanadium. This example is presented to show the somewhat inadequate results obtained through the use of molybdenum trioxide alone, and further that the addition of boric acid, in the absence of phosphoric acid, does not appear to effect a substantial improvement.

Example 11 In this example 0.38 gram of 85% phosphoric acid and 5.76 grams of molybdenum trioxide, a 12:1 molar ratio of molybdenum to phosphorus were added to 200 grams of water and heated to the boiling point for 10 minutes. The finely divided slurry was added to 500 grams of the Wyoming sour crude, containing 250 grams of benzeneand subjected to distillation during the addition. 200 grams of the resulting colloidal suspension, containing 0.8% by weight of molybdenum, was placed in a rotating autoclave at the conditions hereinabove set forth, the resulting normally liquid hydrocarbon portion of the product effluent indicating 1480 p.p.m. of nitrogen, 0.64% by weight of sulfur, 1.00% by Weight of pentaneinsoluble asphaltenes, 0.4 p.p.m. of nickel and 2.3 p.p.m. of vanadium, a substantial improvement over the results of the preceding example.

2.47 grams of boric acid and 4.61 grams of 85% phosphoric acid were placed in a beaker containing 225 grams of water. The solution was heated to the boiling point, and 5.76 grams of molybdenum trioxide were added.

b The resulting solution was concentrated to about 213 grams and added to 500 grams of the Wyoming sour crude, containing 250 grams of benzene, and accompanied by distillation to remove water. The final colloidal suspension contained 0.98% molybdenum, as the element, the molar ratio of molybdenum to phosphorus to boron being 1:121. After maintaining the above-described conditions for a period of 8 hours, the normally liquid hydrocarbon portion of the total product effluent indicated 840 p.p.m. of nitrogen, 0.49% by weight of sulfur, 0.34% by weight of pentane-insoluble asphaltenes, 0.2 p.p.m. of nickel and 0.7 p.p.m. of vanadium.

Example III In this example, 200 grams of the Wyoming sour crude containing 0.8% by weight of molybdenum as a colloidal suspension, and prepared utilizing a molar ratio of molybdenum to phosphorus of 12:1, was maintained within the rotating autoclave at a temperature 400 C., and a pressure of atmospheres, for a period of 8 hours. The normally liquid hydrocarbon portion of the product effiuent contained 1480 p.p.m. of nitrogen, 0.64% by weight of sulfur, 1.00% by weight of pentane-insolubles, 0.4 p.p.m. of nickel, and 2.3 p.p.m. of vanadium. The molybdenum-containing catalyst sludge was admixed with 200 grams of fresh Wyoming sour crude, and the original quantity of phosphoric acid added to the resulting mixture. Following a period of 8 hours in a rotating autoclave at a temperature of 400 C. and a pressure of 200 atmospheres, the normally liquid product effluent indicated 983 p.p.m. of nickel, 0.27% by weight of sulfur, 0.40% by weight of pentane-insoluble asphaltenes, 0.04 p.p.m. of nickel and nil vanadium.

This example is given to illustrate the additional beneficial effects resulting when at least a portion of the catalyst-containing sludge is combined with fresh petroleum crude oil, the phosphoric acid being replaced. There has been indicated substantial improvement over those results obtained when utilizing fresh molybdenum trioxide with phosphoric acid.

The foregoing examples and specification clearly indicate the method of effecting the process of the present invention and preparation of the'catalyst employed therein. It should be noted that there has been a significant degree of elimination and/ or conversion of the various contaminating influences, particularly when molybdenum trioxide was added to the petroleum crude oil in the presence of both phosphoric acid and boric acid. The crude oil has been hydrorefined to the extent that it is extremely suitable for further processing, and the benefits afforded the process of hydrorefining petroleum crude oils through the use of the method of the present invention will be readily recognized by those possessing skill within the art of petroleum refining.

We claim as our invention:

1. A catalyst which comprises a colloidal suspension of molybdenum trioxide and phosphoric acid in a hydrocarbon, the suspension containing from about 0.1% to about 10% by weight of molybdenum, calculated as the element, and the molar ratio of molybdenum to phosphorus being within the range of about 1:1 to about 18:1, calculated as the elements.

2. A catalyst which comprises a colloidal suspension of molybdenum trioxide, phosphoric acid and boric acid in a hydrocarbon, the suspension containing from about 0.1% to about 10% by weight of molybdenum, calculated as the element, and the molar ratio of molybdenum to phosphorus to boron being within the range of from about 121:1 to about 18:1:1, calculated as the elements.

3. A process for hydrorefining a hydrocarbon charge stock which comprises forming a colloidal suspension of molybdenum trioxide and phosphoric acid in said charge stock, the suspension containing from about 0.1% to about 10.0% by weight of molybdenum, calculated as the element, and the molar ratio of molybdenum to phosphorus being within the range of about 1:1 to about 18:1, calculated as the elements, and thereafter reacting said colloidal suspension with hydrogen at a temperature above about 225 C. and at a pressure greater than about 500 pounds per square inch gauge.

4. The process of claim 3 further characterized in that said colloidal suspension is reacted with hydrogen at a temperature Within the range of from about 225 C. to about 500 C. and at a pressure of from about 500 to about 5000 pounds per square inch gauge.

5. A process for hydrorefining a hydrocarbon charge stock which comprises forming a colloidal suspension of molybdenum trioxide, phosphoric acid and boric acid in said charge stock, the suspension containing from about 0.1% to about 10.0% by weight of molybdenum, calculated as the element, and the molar ratio of molybdenum to phosphorus to boron being within the range of from about 1:1:1 to about 18:1:1, calculated as the elements, and thereafter reacting said colloidal suspension with hydrogen at a temperature within the range of from about 225 C. to about 500 C. and at a pressure of from about 560 to about 5000 pounds per square inch gauge.

6. The process of claim 5 further characterized in that said hydrocarbon charge stock comprises a petroleum crude oil containing pentane-insoluble asphaltenes.

No references cited. 

1. A CATALYST WHICH COMPRISES A COLLOIDAL SUSPENSION OF MOLYBDENUM TRIOXIDE AND PHOSPHORIC ACID IN A HYDROCARBON, THE SUSPENSION CONTAINING FROM ABOUT 0.1% TO ABOUT 10% BY WEIGHT OF MOLYBDENUM, CALCULATED AS THE ELEMENT, AND THE MOLAR RATIO OF MOLYBDENUM TO PHOSPHORUS BEING WITHIN THE RANGE OF ABOUT 1:1 TO ABOUT 18:1, CALCULATED AS THE ELEMENTS. 